Boiler heating systems are widely used to heat residential and commercial buildings. A typical boiler heating system includes a boiler, pipes, radiators and water or similar heat transfer fluid. The boiler generates heat from a heat source, such as a resistive heating element or a combustion chamber in which fuel is burned. The heat is transferred to the water, and the heated water is then pumped through supply pipes to radiators located within the interior of a building. Heat from the heated water flowing through the radiators is transferred to the cooler air. The relatively cooler water from the radiator is then returned to the boiler through return pipes to be heated and circulated again through the radiator.
Particular areas of the building, referred to as zones, are heated independently of other zones in the building. Each zone is heated by at least one radiator. A zone valve controls the flow of heated water from the boiler to each radiator in that zone. A thermostat is located in each zone, and the thermostat controls the zone valve for that zone. In this way, each zone valve is controlled independently of the others to allow independent control of the heat within each different zone in the building.
The thermostat and the zone valve for each zone are connected in series with a transformer which provides electrical power to operate those components. The thermostat functions as a temperature responsive switch which closes when the measured temperature of the air falls below a selected temperature and which opens when the temperature is at or greater than the selected temperature. When the thermostat switch closes, electrical power is delivered to the zone valve, causing the zone valve to open, and the open zone valve conducts heated water through the supply pipes to the radiator within the zone. The flow of heated water through the radiator eventually heats up the air within the zone until the temperature of the air within the zone reaches or exceeds the selected temperature. At that point the switch of the thermostat opens, causing the zone valve to close. The closed zone valve terminates the flow of heated water through the radiator. Thus, the thermostat is closed and the zone valve for a particular zone is opened when the temperature within that zone is less than the selected temperature, and the thermostat is open and the zone valve for the particular zone is closed when the temperature within the zone is at or greater than the selected temperature. In this manner, the temperature in each particular zone is regulated and maintained at approximately the selected temperature.
The boiler may include a hot water storage tank in which a supply of hot water is always maintained. The boiler may also heat the hot water for delivery to the radiators whenever hot water is requested by a thermostat. The boiler includes a start switch which activates both the heat source and an internal pump to circulate the heated water. In a situation where the boiler includes a hot water storage tank, the start switch activates the internal pump to circulate the heated water through the zone valves to the radiators, and a separate thermostatic switch associated with the hot water storage tank may control the heat source of the boiler. In the situation where the boiler heats the hot water when the thermostat requests heat, the heat source of the boiler and the internal pump are activated simultaneously by the start switch. An end switch is connected to each zone valve, and the end switch closes when the zone valve is opened. The boiler start switch is connected in parallel with all of the end switches of the all of the zone valves. Connected in this manner, the start switch is closed and the internal pump (and possibly the heat source) are operated when any one of the zone valves is opened by the thermostat.
Properly connecting the end switches, the boiler start switch, the thermostats in each zone and the zone valves is typically one of the most difficult wiring tasks for a technician to learn. Many hours are typically expended in training technicians to properly wire the different components of the boiler heating system. One of the factors that contributes to the difficulty in learning to correctly connect the components of the boiler heating system is a lack of organization of the wires connecting the components. Usually, these wires are not labeled and often must be traced to the boiler start switch, the transformer, the thermostats and the zone valves, in order to determine which wires are connected to what components. Even experienced technicians can spend a significant amount of time determining the wiring configuration. The time spent trying to determine which roles the connecting wires in a boiler heating system play adds extra cost to service calls. The cost to install a typical boiler heating system is also more expensive due to the lack of organization and clear identification of the electrical conductors which connect the boiler heating system components.